The present invention relates to a minimally-invasive implant for the purpose of opening and enlargement of a processus spinosus interspace, and particularly an interspinous process spacer for enlarging the spinal canal.
The spinal canal is a cylindrical space in a vertical direction located in the center of a backbone (corpus vertebrae), and a spinal cord and cauda equina (nerve) are housed therein and protected firmly. Spinal canal stenosis where this spinal canal is stenosed due to various causes such as deformation of a bone, a cartilage or a ligament to press the nerve therein has become a major social problem as the number of patients has increased in conjunction with an aging society.
In particular, lumbar spinal canal stenosis refers to a state where the deformation and thickening of lumbar vertebra and intervertebral joints as well as deformation and bulging of the intervertebral disc which is cartilage tissue, or hypertrophy of a ligament occurs and these make the spinal canal narrow to apply pressure or squeeze the nerves and blood vessels. This symptom is typified by a gait disorder such as neurogenic intermittent claudication, and this symptom is characterized in that a lower limb does not advance forward after walking for a few minutes and when taking a rest by crouching, subsequently the patient can walk again. In addition, sciatic neuralgia, lower limb symptoms such as palsy, a cold sensation and a feeling of lassitude, lumbar pain and urinary bladder and rectal disorders (disorders of urination and defecation) and the like are lumbar and lower limb symptoms of lumbar spinal canal stenosis.
It has been known that lumbar and lower limb symptoms due to lumbar spinal canal stenosis are anatomically reduced and improved by anteflexion of the lumbar vertebra, e.g., crouching or riding a bicycle.
As conservative therapeutic methods which improve symptoms in daily life, physical therapies such as drug therapy of administering a drug which is a vasodilator drug or increases blood flow to a nerve root or a periphery of the cauda equina, an epidural block method, a radicular block method, an orthosis therapy of wearing a lumbar vertebra bending position corset to keep the lumbar portion at rest at the bending position, and an ultrasonic therapy and a hot pack therapy for improving pain relief, muscular spasticity and blood circulation are available.
When conservative therapy is ineffective and severe neurological disorder and intermittent claudication sustain, a surgical therapy countering this conservative therapy is available, and neurological decompression procedures such as a laminectomy and expanded fenestration have been conventionally performed. In the laminectomy and expanded fenestration, surgical invasion is applied to the patient to restore the lumbar vertebra stenosis site, and thus it is necessary to give general anesthesia to the patient. In this procedure, the patient is likely to be exposed to the risk of hemorrhaging and serious complications, and hospitalization for several days to several weeks is required for a patient after the operation. Therefore, this procedure heavily burdens the patient, and particularly when the patient is elderly, the symptom is sometimes further worsened.
However, in recent years, it has been reported that by stationing an interspinous process spacer in a minor surgical method, the effect of local lumbar anteflexion is obtained and satisfactory results are obtained (See International Application No. 2005-517467 and Sekitsui Sekizui Shinkei Shujutsu Shugi 6(1):120-123, 2004, “Therapeutic experiences of lumbar spinal canal stenosis by interspinous process spacer (Sten-X™) performed under local anesthesia.”).
Also, as the interspinous process spacer, the spacer inserted in the processus spinosus interspace using a guide pin and an obturator is publicly known (See WO 2005/072301).
Such a minimally invasive procedure can be performed under a local anesthesia. Thus, a shorter period is needed for recovery, there is almost no hemorrhaging, the risk of serious complications is reduced and therapeutic cost required for the patient is less. Therefore, it has been desired that spinal canal stenosis can be treated using the minimally invasive procedure.
As described above, it has been reported that by stationing the interspinous process spacer, the effect of local lumbar anteflexion is obtained and satisfactory results are obtained. A prior and existing spacer device used for this is described with reference to FIGS. 1A-1D. FIGS. 1A-1D show an entire schematic view and a use example of the prior and existing spacer device. FIG. 1A shows a completed view of an assembly of the spacer device, FIG. 1B shows an appearance where one wing region has been removed in the spacer device, FIGS. 1C and 1D show the appearances before and after attaching the spacer device. In the prior and existing spacer device 30, as shown in FIG. 1A, the wing regions 32 are constituted by pinching the spacer region 31, and as shown in FIG. 1B, one wing region is detachable.
Such a spacer device is disposed in the stenosed processus spinosus interspace as shown in FIG. 1D to enable enlarging and fixing the processus spinosus interspace.
In such a spacer device 30, as shown in FIGS. 2A-2D, a part of a back of a patient is cut open by means of surgical operation, the paraspinal muscle is detached, the processus spinosus and interspinous ligament are exposed (FIG. 2A), first a specialized device is inserted in the processus spinosus interspace to provide a hole in the processus spinosus interspace (FIG. 2B), subsequently the spacer device is inserted in the processus spinosus and screwed into the processus spinosus interspace (FIG. 2C), and finally the wing region is placed from above and fixed with a screw (FIG. 2D). Thus, in the operation using this device, a minimal skin incision of about 3 cm or more is required, and it is necessary to detach the paraspinal muscle from the spine.
Such a procedure may be possible under local anesthesia but is difficult. Further surgical invasiveness is never minor.
In the interspinous process spacer disclosed in WO 2005/072301, in order to insert the spacer in the processus spinosus interspace, it is required to first insert the guide pin from the skin incision site, subsequently the obturator is inserted which covers it to enlarge the processus spinosus interspace and finally insert the spacer. This obturator has a large diameter, thereby functioning to construct a path from the skin incision site to the processus spinosus interspace for inserting the spacer. However, in insertion of such an obturator, if the processus spinosus interspace is enlarged smoothly, it is required to insert the obturator by sequentially changing the diameter from small to large. Thus, the patient is heavily burdened and simultaneously the operator is burdened because of multiple procedures.